Process for the production of high molecular weight polyamides from n - carbaryloxy amino carboxylic acids



United States Patent Int. (:1. 068 20/00 U.S. Cl. 260-78 3 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a process for the production of high molecular weight polyamides by homopolycondensation of N-carbaryloxyaminocarboxylic acids at elevated temperatures, said process being carried out in the presence or in the absence of organic solvents.

The present invention relates to a process for the production of high molecular weight polyamides by polycondensation of N-carbaryloxy-aminocarboxylic acids.

It is known to prepare polyamides by reacting polymethylene-bis-carbamic acid alkyl or aryl esters with aliphatic dicarboxylic acids. Polyamides may also be obtained from derivatives of aliphatic a-amino acids for example by the reaction of N-carbophenoxyglycine to form the polypeptide of glycine.

It is an object of this invention to providea process for the production of polyamides, which comprises polycondensing N-carbaryloxy-aminocarboxylic acids at temperatures between 100 and 450 C.

Hydroxyaryl compounds and carbon dioxide are split off in the process. The condensation reaction leads rapidly to formation of high molecular weight products which, depending upon the choice of starting compounds, can be worked up into moulded articles, films, foils, coatings and filaments. This process possesses the advantages over the known process that the preparation of the high molecular weight products requires only one starting component in which the reactive groups are always present in the ideal proportion to each other and that the reaction proceeds very rapidly and practically quantitatively, so that the process is especially suitable for continuous operation. A further advantage is that the starting compounds can be obtained in a particularly pure state since they can easily be crystallised from organic solvents, as compared with the purification of amino acids commonly used as starting materials which may often be diificult if these are to be polymerised to high molecular weight products by known processes.

It is also surprising that polymerisation of N-carbaryloxy-w-aminocarboxylic acids proceeds at high reaction velocities and in high yields since the known reaction of N-carbophenoxy-glycine to give the polypeptide of glycine results in a yield of only about 17% after a reaction time of 400 hours. Owing to the high degree of conversion in the process according to the invention very small quantities of extract are obtained; this leads to an improvement in the desired properties for use of the polymers.

The process according to the invention can be carried out in solution or in the melt, thus widening the range of application. According to earlier proposals of the applicants, N-carbaryloxy-aminocarboxylic acids can be prepared by reacting an aminocarboxylic acid with a diarylcarbonate or by reacting a trialkylsilyl ester of an amino acid with a chloroformic acid aryl ester.

For example, aminocaproic acid may be reacted with diphenyl carbonate at temperatures of about C. to form N-carbophenoxy-G-aminocaproic acid. Alternative- 1y, trimethylsilyl 2-aminobenzoate, for example, can be reacted with phenyl chloroformate in an inert organic solvent to form N-carbophenoxy-Z-aminobenzoic acid.

The following compounds are specific examples of compounds which may be used in the process according to the invention: N-carbophenoxy-3-a1ninobenzoic acid, N-carbophenoxy-4-aminobenzoic acid; N-carbophenoxy- 3-amino-4-methyl-benzoic acid; N-carbophenoxy-S-amino- 4-ch1or0-benzoic acid; N-carbophenoxy-4-amino-3-methoxy-benzoic acid; N-carbo-(4'-chlorophenyloxy)-3-aminobenzoic acid; N carbo-(4'-tertiary butylphenyl)oxy-3- aminobenzoic acid; N carbophenoxy-3-aminophenylacetic acid; N-carbophenoxy-4-amino-phenylacetic acid; N- carbophenoxy B-(3-aminophenyl) isobutyric acid; N- carbophenoxy-3-aminocinnamic acid; N-carbophenoxy-3- aminopropionic acid; N carbophenoxy 6-aminocaproic acid; N-carbophenoxy-ll-aminoundecanoic acid; N-carboxy-(4-chlorophenyl)oxy-fi-amino-caproic acid and N- carb-(4-tertiary butylphenyl)oxy-tS-aminocaproic acid.

The polyamides prepared by the process contain the following repeating structural unit:

wherein A is an aromatic, aliphatic or araliphatic radical which may be substituted.

The process may be carried out by heating N-carbaryloxy-aminocarboxylic acid at temperatures of 100 to 250 C. in an apparatus equipped with stirrer, and completing the reaction at temperatures of 200 to 450 C., if desired under reduced pressure. In another method of carrying out the process according to the invention, poly-condensation is carried out in solution, In this case, the N-carbaryloxy aminocarboxylic acids are heated at temperatures of to 350 C., if desired with application of pressure, in 5 to 100 times their quantity of an organic solvent which may contain quantities of inorganic salts, and the reaction time is adjusted so that viscous solutions are obtained which can then immediately be spun or cast to form films, or from which the polymer can be precipitated by the addition of non-solvents such as water. Solvents which may be used in this method of carrying out the process are, for example, formamide, N,N-dimethylformamide, N,N dimethylacetamide, N-methylcaprolactam, N-methylpyrrolidone, tetramethylene urea, N-formyl morpholine, N-acetylmorpholine, pyridine or quinoline. Inorganic salts which may be added include lithium chloride, magnesium chloride, calcium, chloride and zinc chloride.

EXAMPLE 1 0.1 mol of N-carbophenoxy-3-a.minobenzoic acid was heated in a condensation apparatus equipped with stirrer for 60 minutes under a pressure or 10 mm. Hg, the temperature being initially 220 C. and subsequently increased by 20 C. at intervals of 15 minutes. Carbon dioxide is given oil and 0.1 mol of phenol distills off within the first 5 minutes. A pale coloured product remains behind as residue which has a relative viscosity of 1.16 measured in concentrated sulfuric acid at 25 C. with c.=1 g. in 100 ml.

Preparation of N-carbophenoxy-3-aminobenzoic acid 246 g. of a mixture of 50 mol percent 3-aminobenzoic acid and 50 mol percent N-trimethylsilyl-3-aminobenzoic acid trimethylsilylester, dissolved in l l. methylenechloride are reacted with 157 g. chloroformic acid phenylester, dissolved in 150 ml. methylenechloride, in the presence of 129 g. quinoline at 0 C. by adding the choloroformic phenylester solution dropwise. When the reaction is finished, the mixture is evacuated and the residue dissolved in 1 l. benzene and 35 g. methanol are added. After standing overnight the precipitated crystals are filtered off and recrystallised from toluene/alcohol.

4 carbophenoxy-3-aminobenzoic acid, (c) 0.1 mol of N- carbophenoxy-6-aminocaproic acid, and (d) 0.1 mol of N-carbophenoxy-ll-aminoundecanoic acid were heated in the solvents and additives indicated in Table 2 at the temperatures indicated therein. Polymers were formed within 231 g. N-carbophenoxy-3aminobenzoic acid are obtained, 5 the times indicated while 0.1 mol of carbon dioxide was M.P. 240 C. (decomposition). split off. Formation of these polymers was indicated by the increase in solution viscosity. The polyamides could EXAMPLE 2 then be precipitated as colourless powders from these solu- 0.1 mol of N-carb-(4'-chlorophenyl)oxy-3-a i b tions by the addition of 100 ml. of water. The yields and zoic acid were condensed at 300 C. under a vacuum of relative viscosities of the products obtained are also 10 mm. Hg for 13 minutes in the same apparatus as that shown in the table.

TABLE 2 Reaction Reaction Yield temp. time percent of Example 4 Solvent Additive C.) (11.) theory "Irel c.=1 g./l00 ml.

(a) 130 g. N,N-dimethylaeetamide 5 g. lithium chloride. 165 0. 33 95 1.12/sulphuric acid. (b) 115 g. N,N-dimethylformamide 11 g. zinc chloride... 155 2 05 1.07/sulpliuric acid. (c) 130 g. N,N-dinethylacetamide. 5g.lithium chl0ride 165 0.5 95 2.30/m-ci'esol. (d) 130 g. N,N-dimethylacetamide-... 5g. lithium chloride. 165 0.5 95 2.1/ni-cres01,

used in Example 1. 0.1 mol of phenol distills oft sponta- What we claim is: neously. The relative viscosity of the product obtained is 1. A process for the production of film forming poly- 1.21 measured in concentrated sulfuric acid at C. amides which comprises poly-condensing at least one N- c.=l g. in 100 ml. The N-earb-(4'-chlorophenyl)oxy-3- 9r Carbaryloxyamino carboxylic acid selected from the group aminobenzoic was prepared analogous to the method for consisting of N-carbophenoxy-3-aminobenzoic acid, N- the preparation of 3-carbophenoxy aminobenzoic acid. carb0phenoxy-4-aminobenzoic acid, N-carbophenoxy-3- EXAMPLE 3 amino-4-methyl-benzoic acid, N-carbophenoxy-3-amino- 4 chloro benzoic acid, N carbophenoxy-4-arnino-3- 11101 of N-cafbophenoxy-4-amiflobenloic acid, methoXy-benzoic acid, N-carbo-(4'-chlorophenyloxy)-3- 01 R101 0f P y- P Y 3O aminobenzoic acid, N-carbo-(4-tertiary butylphenyl)oxyacid, mol of N'CETbOPh6BOXY-6-amin0CaPr0i 3 aminobenzoic acid, N carbophenoxy-3-aminophenylacid, and (d) 0.1 mol of N-carbophenoxy-llmin nacetic acid, N-carbophenoxy-4-aminophenylacetic acid, decanoic acid were condensed under the conditions indi- N arbophenoxy-fi-(3-aminophenyl) isobutyric acid, N cated in Table 1 in the apparatus described in Example 1. r b h 3- i i i id, N b h -3. The relative viscosities and extract contents are also aminopropionic acid, N carbophenoxy 6-aminocaproic shown in the table. acid, N-carbophenoxy-ll-aminoundecanoic acid, N-carboxy-(4-chlorophenyl)oxy-6-aminocaproic acid and N- Prepamnon of carbophenoxy 4 amln?benzolc acld carb-(4-tertiary butylphenyl)oxy-6-aminocaproic acid at A mixture of 200 g. phenol, 321.3 g. diphenylcarbonate 40 temperatures between 100 and C. and 137.1 g. p-aminobenzoic acid are heated for 4 hours The process of Claim 1, Said polycondensing being at 120 C. Thereafter 250 g. phenol are distilled off at carried out in an Organic Solvent 0.2 mm. Hg. The residue is several times extracted with The process of claim 2 Said organic solvent contaim chloroform. 226.5 g. N-carbophenoxy-4-aminobenzoic ing inorganic salts acid are obtained. M.P. 250 C. (decomposition).

The N-carbophenoxy-6-aminocaproic acid (M.P. 113 References Clted C.) and the N-earbophenoxy-ll-aminoundecanoic acid UNITED STATES PATENTS (M.P. 88 C.) are obtained in an analogous manner. 2,071,253 2/1937 Carothers 260 78A The N-carbophenoxy 4-amino-phenyl acetic acid (M.P. 2,688,011 8/1954 Wheattey et aL 108 C.) is obtained analogous to the method given in 2,368,770 1/1959 Temin Example 3,109,836 11/1963 Berry 260-78A TABLE 1 3,232,910 1/1966 Preston 26078A Extract 3,350,365 10/1967 Wakasa et a1. 26078A T emp. Pressure Reaction 1 1 0 1 (ciiritggt; 3,408,334 10/1968 Caldwell et al. 26078A Example3 C.) (mm. Hg) time(min). s. 1g./10 p c FOREIGN PATENTS (a) 300 1.0 30 1.10/sulphur1c aci 1,100,951 3/1961 Germany 26078A if 53 0 857,657 1/1961 Great Britain 260-78A (c) 275 0.9 20 2.33/m-cresoL. 0.75 1,008,644 11/ 1965 Great Britain 260-78A (d) 280 1.0 20 2.50/m-cresol 1.0

*Extracted with methanol at O.ior 24 hours. 60 OTHER REFERENCES Chem. Abst., 521162290, Liwshitz et al., Polymeriza- EXAMPLE 4 tion of N-Carbobenzoxy Amina Acid. Example 4 describes the condensation of N-carbaryl- Chem- Abstw 5355149f, I $h1Zuka, Allaoxyaminocarboxylic acids in solution. In a 250 ml. glass logs: X Polycondensatlon Methodfiask equipped with reflux condenser and a connection for controlling inflow of gases, (a) 0.1 mol of N-carbo phenoxy-4-aminophenylacetic acid, (b) 0.1 mol of N- HAROLD D. ANDERSON, Primary Examiner E. WOODBERRY, Assistant Examiner 

